<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<script>
var arr1 = [1,2,3];
var arr2 = [];

	for(var i=0; i < arr1.length; i++)
	{
			arr2.push(arr1[i]);
	}
	arr2.push(4);
	
	alert(arr1);
	alert(arr2);
	
</script>
</head>

<body>
</body>
</html>
